(1) Field of the Invention
The present invention generally relates to an array plate for use on underwater vehicles.
(2) Description of the Prior Art
Presently, underwater or undersea vehicles employ sonar arrays to find, localize, avoid, and classify underwater objects. Such vehicles typically use forward-looking sonar arrays that have acoustic transducers or other sensing elements attached to an array plate or baffle. The performance of these sonar arrays is often degraded by the self-noise generated by the underwater vehicle itself.
Typically, this self-noise is in the form of vibrations that are produced by the propulsion system of the underwater vehicle. The self-noise travels through the structure of the underwater vehicle and through the array plate to which are attached the acoustic transducers. As a result, the vehicle self-noise causes an increase in the noise floor and adversely affects the performance of the acoustic transducers.
In many operations, passive sonar arrays are used instead of active sonar systems. Passive sonar arrays use sensing elements, such as piezoelectric elements, to sense pressure fluctuations in the water which represent sound. However, the amplitude and power levels of acoustic signals detected by passive sonar arrays are very low; thus, the vehicle self-noise can significantly degrade the performance of the passive sonar array in the detection of such low-level acoustic signals. Active sonar array systems are also affected by vehicle self-noise.
In order to achieve improvement in the performance of the sonar array, isolation techniques have been used isolate the sonar array from the vehicle self-noise. A review of the prior art reveals several references that disclose a variety of array plate structures and noise-isolation configurations for use with acoustic transducers.
Cook et al. (U.S. Pat. No. 4,004,266) discloses a transducer array with low cross coupling. Each transducer is set in the recess of a steel baffle plate.
Hodges et al. (U.S. Pat. No. 4,192,246) discloses a torpedo nose section having an acoustic window and nose section interfacing with the main body of a torpedo at a position aft of acoustic transducers positioned in the nose section.
McQuitty et al. (U.S. Pat. No. 4,949,317) discloses a compliant baffle for attachment to a rigid transducer mounting plate. The baffle is coupled to one side of the plate and the transducers are coupled to the opposite side of the plate.
Madden et al. (U.S. Pat. No. 5,426,619) discloses a mounting arrangement for a sonar array. A three-layer plate is coupled to a steel plate by means of compliant material tubes. Transducers are mounted on one plate layer and Madden et al. (U.S. Pat. No. 5,428,582) discloses a decoupling ring that surrounds a sonar array and serves as the interface with the nose of an underwater vehicle.
Dubois (U.S. Pat. No. 5,905,693) discloses a vibration isolation mount for an acoustic device. The mount is constructed in “layers” with a rigid mount supporting the acoustic device, a compliant collar coupled to the rigid mount, and a rigid mount positioned between the other end of collar and the structure to which the mount is coupled.
Dubois (U.S. Pat. No. 5,992,077) discloses a multi-layered nose cone assembly for surrounding and shielding a sonar array mounted in the nose portion of an underwater vehicle.
Based on the prior art references, a need still exists for an improved isolation device that significantly reduces the magnitude of vehicle self-noise that reaches the array plate and the acoustic transducers.